#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int print(int arr[],int len)
{
	int danshengou = arr[0];
	for (int i = 1; i < len; i++)
	{
		danshengou ^= arr[i];
	}
	return danshengou;
}

int main()
{
	int arr[] = { 1,2,3,4,5,1,2,3,4 };
	int len = sizeof(arr) / sizeof(arr[0]);
	int ret=print(arr,len);
	printf("%d\n", ret);
	return 0;
}